Method for transmitting data from applications with different quality

ABSTRACT

The invention relates to a method for transmitting data of applications with different quality requirements in a packet-oriented data communication network that comprises communication nodes. The inventive method comprises the following steps: a) limiting the data of every application to a defined bit rate in a communication node to be passed during transmission of the data of the respective application; b) generating and storing application-specific contexts in all communication nodes to be passed during transmission of the data of the respective application; c) reserving, in line with the application-specific contexts, transmission resources in all communication nodes to be passed during transmission of the data of the respective application; d) forwarding, in line with the application-specific contexts, the data of every application from a communication node to be passed by the respective application to another communication node to be passed.

CLAIM FOR PRIORITY

This application claims priority to International Application No.PCT/DE01/04724 which was published in the German language on Jul. 3,2003, and filed in the German language on Dec. 10, 2001.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a method for transmitting data fromapplications with different requirements in terms of the quality of atransmission service in a packet switched data communication network.

BACKGROUND OF THE INVENTION

A fundamental feature of packet switched data communication networks isthat data transmission takes place not via dedicatedly connected datapaths, but rather via virtual data paths according to the principle ofrandom multiplexing. In this context, multiplexing is understood to meanthe simultaneous transmission of a plurality of information items viathe same transmission path on the basis of the random distribution ofthe various information items over time. The data which are usuallytransmitted in such networks are distinguished by a “burst”characteristic, i.e. by fluctuations in their bandwidth over time. Inorder to be able to transmit the data effectively, they are generallyaggregated between communication nodes in the packet switched datacommunication network, and statistical assumptions are used to transmitthem together from communication node to communication node via existingtransport paths, i.e. via virtual data paths. There is no exclusiveprovision of transmission resources for individual applications on an“end to end” basis. The random multiplexing makes effective use of theexisting transmission resources. In contrast, in circuit switched datacommunication networks, each application is provided with a dedicatedpath through the data communication network, on which both thetransmission time and the bandwidth are guaranteed. If data aretransmitted at a variable bit rate in this case, the available bandwidthis not exhausted in the case of pauses or periods in which thetransmission rate is low.

Any application in a mobile packet switched data communication networkdemands particular resources for the transfer capacity from the datacommunication network for the duration of the application, in order toallow “end to end” communication. In mobile packet switched datacommunication networks, this is done by applying a “context” with anappropriate set of parameters at every affected communication node whichneeds to be encountered. A context contains all of the relevantinformation which provides an adequate description of the servicerequired for transmitting the data. In particular, each applicationrequires a particular transmission service in a particular quality(QoS—Quality of Service) from the data communication network. Thisrequirement is characterized by “QoS parameters”, such as a maximum bitrate, a guaranteeable bit rate and a maximum permissible delay. When acontext is created, each communication node negotiates these QoSparameters in line with its existing resources, with the parameters eachbeing negotiated in stages. The respective application's data are thentransmitted on the basis of these negotiated and stored QoS parameters,which are the same at all of the communication nodes which are to beencountered.

To date, the problem of transmitting data from applications withdifferent requirements in terms of the quality of transmission has beensolved in different ways.

There is a QoS architecture from the 3GPP (TS 23.107) which describesparticular QoS functions for 3rd generation (UMTS) mobile radionetworks. Implementation at individual communication nodes is notspecified in more detail, however. In addition, there are approacheswhich describe methods for transmitting data from applications withdifferent QoS requirements in a data communication network.

A first approach involves providing each data packet with informationabout the demanded transmission quality. In this case, particularquality classes, which provide a suitable reflection of the transmissionrequirements, are defined in a data communication network. These classesare then called Quality of Service classes. Each data packet is assignedto a QoS class and is provided with corresponding information. Eachcommunication node (which forwards data in such a data communicationnetwork) which is to be encountered prioritizes the forwarding of a datapacket on the basis of the QoS information which each data packetcontains. In this case, the usual treatment is to distribute packets inappropriate queues according to the QoS information these packetscontain. These queues are emptied and forwarded at different speedsaccording to their QoS class. This approach statistically increases theprobability of a high priority data packet being routed through the datacommunication network much more quickly than a data packet with lowpriority. A drawback of this approach is that there is no guaranteedtransmission time and transmission rate within the data communicationnetwork. Other drawbacks are that data packets requiring transmission inreal time are buffer stored in every queue and are thus delayed. Anotherdrawback is that the information about the association with a QoS classneeds to be contained in every data packet and that the format of thisinformation needs to be the same throughout the data communicationnetwork. This approach is described, by way of example, in the RFC 2474standard from IETF (Internet Engineering Task Force).

A second approach to solving the problem described above involvessetting up different data paths within the data communication networkfor each QoS class. If a communication node is able to associate a datapacket with a QoS class, this data packet is forwarded on a data pathwhich corresponds to this QoS class.

A drawback of this method is the costs for setting up and operating alarge number of different paths of different quality between differentcommunication nodes. The setup of different paths in different QoSclasses has been defined in various standards, for example in theTraffic Management Specification, also called AF-TM-0121.000 by the ATMforum.

A third approach involves limiting the total traffic at the access nodeinto the data communication network, an “edge node”, to a predefinedtraffic level. This traffic level will then not differ again within thedata communication network, since it is presupposed that the datacommunication network has adequate dimensions. The drawback of thisapproach is the lack of any guarantee with regard to transmission timeand transmission rate. This approach is specified by the IETF's ServiceLevel Agreement Working Group, for example.

SUMMARY OF THE INVENTION

The present invention relates to a method for transmitting data fromapplications with different requirements in terms of the quality of atransmission service in a packet switched data communication network. Inpacket switched data communication networks with, by way of example, IPbased transmission mechanisms, different data types from variousapplications are transmitted from a source to a destination via anetwork. In this context, the requirements in terms of the manner oftransmission between various applications vary greatly. This appliesparticularly to the transmission of data from applications which requiretransmission in real time and/or using a guaranteed bit rate, ascompared with transmission of data which are not subject to stringentrequirements in terms of transmission in real time and/or in terms of aguaranteed bit rate. Applications requiring transmissions in real timeand with a guaranteed bit rate are, by way of example, voice telephony,online radio and video transmission. By contrast, electronic mailservices or Internet applications, such as web surfing, have nocomparable requirements in terms of transmission.

The present invention provides a method which can be used to transmitdata from applications with different transmission requirements withinthe data communication network as efficiently as possible and avoidingthe above drawbacks.

In one embodiment of the invention, there is a method for transmittingdata from applications with different transmission requirements in apacket switched data communication network containing communicationnodes, including:

-   -   a. each application's data are limited to a prescribed bit rate        at a communication node which is to be encountered when a        respective application's data are transmitted,    -   b. application specific contexts are created and stored at the        communication nodes which are to be encountered when a        respective application's data are transmitted,    -   c. transmission resources are reserved at the communication        nodes which are to be encountered when a respective        application's data are transmitted, in line with the application        specific contexts,    -   d. each application's data are forwarded from a communication        node which is to be encountered by the respective application to        a further communication node which is to be encountered, in line        with the application specific contexts.

In one preferred embodiment of the invention, (a) is performed at anaccess communication node (edge node) to the packet switched datacommunication network. An incoming stream of data from an application islimited to a prescribed, preferably to a maximum permissible bit ratewhich is determined by the resources existing in the data communicationnetwork. This ensures that there is no longer any possibility ofimpermissible excess at the subsequent communication nodes which are tobe encountered in the data communication network.

Preferably, each application's data are limited to a prescribed bit rateby measuring the volume of a respective application's data over asettable time interval in parallel with the forwarding of these data andcomparing it with the volume of data which corresponds to the prescribedbit rate. This means that, over a particular interval of time(measurement interval), the size of incoming data packets is summed inparallel with their forwarding. This value reflects the volume of datawithin this time interval. If, by way of example, the maximumpermissible volume of data corresponding to the maximum bit rate is nowreached in this time interval, then this information may be used todecide whether subsequent data packets are rejected or are possiblytransported further, since the communication node's total resourcespermit this. At the start of the subsequent measurement interval, thesize of the data packets starts to be summed again, this summation alsobeing able to start from a start value which is not equal to zero, forexample in order to take into account previous bursts. Hence, firstlyany delay in the data packets is minimized and secondly the negotiateddata rate is prevented from being exceeded at the subsequentcommunication nodes. At the same time, all other communication nodes inthe data communication network which are to be encountered on this datapath no longer need to monitor the maximum permissible bit rate.

In one preferred embodiment of the invention, each communication nodewhich is to be encountered by a respective application's data uses aguaranteed bit rate, required by the respective application, and amaximum supportable bit rate to derive a bandwidth value for atransmission resource which is to be reserved, and reserves thistransmission resource.

In another preferred embodiment of the invention, the method isperformed for data from applications which require transmission in realtime. This means that, when setting up a context for an applicationrequiring real-time transmission (real-time application), eachcommunication node which is to be encountered takes a requestedguaranteed bit rate and the maximum supportable bit rate and derives aparticular bandwidth value for a resource (B_(RealAppl)) which is to bereserved and reserves this bandwidth for this application. Thecalculation of the bit rate which is to be reserved can also take intoaccount measurements relating to the actual resource requirement ofapplications which are active and which have been active. In general, aparticular share of the resources (B_(SumReal)) in the totaltransmission width B_(total) is reserved for the total real-time trafficat the communication node. This means that the bandwidth value(B_(RealAppl)) ascertained for the application is taken from the shareB_(SumReal) which is reserved for the real-time traffic. This means thatthe application has the bandwidth B_(RealAppl) at the communication nodeavailable. When the application has ended, these reserved resources arereleased again. The share B_(SumReal) reserved for real-time traffic ispreferably chosen to be smaller than the total bandwidth at thecommunication node. This ensure that firstly a particular share of theresources is available for applications which do not require real-timetransmission (nonrealtime application), and secondly brief excesses overthe reserved bandwidth (bursts) can likewise be transmitted for realtimeapplications. For applications which do not require real-timetransmission and without a guaranteed bit rate, no bandwidth is reservedfor a single application. Instead, the unreserved share B_(SumNonReal)of the total resources is reserved for such applications(B_(SumNonReal)=B_(total)−B_(SumReal)). At the same time, applicationswhich do not require real-time transmission are also able to use theresources which are reserved for real-time applications but aretemporarily not being used for these. Random multiplexing can be used totransport data from this application with a particular probability. Ifthe actual volume of data in the non-real-time traffic exceeds thebandwidth which is available for the traffic, this traffic is delayed orrejected. The actual sum of data to be transported for the real-timeapplications may exceed the resources reserved therefor. This is thecase, for example, when data streams having the maximum bit rate arriveat the communication node at the same time for all or a large number ofreal-time applications, and a smaller bandwidth has been reserved forthese services. When this case arises, portions of the resourcesprovided for non-real-time applications are used concurrently fortransporting the real-time applications' data. A correspondingly smalleramount of resources is then available for the data transmission fornon-real-time applications. The share of reserved resources B_(SumReal)and the calculation algorithm for the bandwidth which is to be reservedgovern the extent to which the real-time applications' data may exceedthe reserved resources and how high the probability is that data fromnon-real-time applications will be transported. In this case, the numberof randomly multiplexed data streams for the applications, inter alia,may also be of significance. The larger the reserved share for real-timeapplications, the lower the probability that temporary excesses (bursts)over the reserved bandwidth will be able to be transmitted. The largerthe share of the reserved share for real-time applications, the lowerthe probability that data from non-real-time applications will betransported.

In one preferred embodiment of the invention, this behavior can beinfluenced when activating a context, i.e. when negotiating the QoSparameters. When the application specific contexts are created at eachcommunication node, the ratio of a guaranteed bit rate required by therespective application and a maximum supportable bit rate can preferablybe varied and hence restricted.

In line with the invention, under particular assumptions, it is alsopossible to transmit data for real-time applications up to the maximumguaranteed bit rate B_(maxRealAppl) at each communication node withoutjams forming or data packets being rejected when these data and theguaranteed bit rate are transmitted. Firstly, bursts, i.e. brieftransmission at high bit rates, should occur in randomly distributedform. There will then be a high probability that the sum of the reservedbandwidth B_(SumReal) will not be exceeded. In the event of excesses, aportion of the resources which has been reserved for non-real-timeapplications will be used concurrently. In this case, the sum of themaximum bit rate for all contexts the total resources at a communicationnode must not exceed a measure determined on the basis of ordinaryproportioning methods.

In another preferred embodiment of the invention, the method involvesthe applications' data being classified into at least two categories inline with the application specific contexts and being forwarded in linewith these categories. These two categories advantageously represent atleast the classification into real-time applications and non-real-timeapplications. This categorization is preferably performed at eachcommunication node and, as already mentioned, takes place on the basisof the contexts which exist at the communication node. Each data packetwhich has been assigned to a real-time application is forwarded to thenext communication node immediately without buffer storage. Packetswithout any real-time requirement can be buffer stored in queues and canbe forwarded from the queue in line with a particular reading mechanism.This reading mechanism is able, by way of example, to distribute theavailable transfer resources for the total non-real-time traffic or forportions thereof according to a predefined scheme or is able toimplement simple prioritization for the queues. In this case, theavailable transfer resources for the non-real-time data are dependent onthe instantaneous data volume in the real-time data.

One particular advantage of the present invention is that by combiningthe mechanisms described, such as reservation of transfer resources,limiting of data streams for individual applications to the maximum datarate, and prioritization of various categories of aggregated datastreams when handling and transporting these data streams, it ispossible to ensure transmission which is as effective as possible and isaligned with the individual requirements of a wide variety ofapplications.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages of the invention are presented with the aid of thefigures below, in which:

FIG. 1 shows a block diagram for illustrating an embodiment of theinvention.

FIG. 2 shows a block diagram for illustrating another embodiment of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a block diagram to describe a possible way of limiting datafor an application to a prescribed bit rate. An application's data reachthe data communication network 1 via an access node (edge node) 2. Toachieve the shortest possible delay at the edge node 2 and to dispensewith buffer storage for the purpose of ascertaining the bit rate of theincoming data, this behavior can be produced in the following manner:over a particular interval of time (measurement interval), the size ofincoming data packets is summed in parallel with their forwarding, asindicated by the “uplink” direction arrow, this situation being shown ingraph 3. This value reflects the volume of data in this time interval.If the maximum permissible volume of data corresponding to the maximumbit rate B_(max) is reached within this interval, then this informationcan be used to decide whether subsequent data are rejected, as shown ingraph 4, or are possibly transported further, since the total resourcesat the edge node 2 allow this. The same mechanism is effected in theopposite direction, i.e. in the “downlink” direction. At the start of asubsequent time interval or measurement interval, the size of the datapacket is summed again, with this summation also being able to startfrom a start value which is not equal to zero, for example in order totake bursts into account. This firstly minimizes the delay for the datapackets and secondly prevents the negotiated data rate from beingexceeded at subsequent communication nodes 5. At the same time, allother communication nodes 5 which are to be encountered no longer needto monitor the maximum bit rate B_(max).

FIG. 2 shows a block diagram for schematically illustrating step d. inan embodiment of the inventive method. It shows data packets 6 fromvarious applications being forwarded through a data communicationnetwork 1 which comprises a plurality of communication nodes 7. When anapplication is requested, the communication nodes 7 in the datacommunication network 1 which are to be encountered by the requestedapplication's data or data packets 6 create a context which contains,inter alia, the transmission quality (QoS) which is to be requested forthe application. This requirement is determined by various parameters.These include, inter alia, a maximum bit rate, a guaranteed bit rate anda maximum permissible delay. A data packet 6 arriving in the datacommunication network 1 from an application is now assigned to one oftwo categories 8, 9 at the communication nodes 7 which are to beencountered, in line with the context created and stored at therespective communication nodes 7. In the example shown, the twocategories 8, 9 correspond to a classification into real-timeapplications (black stripe) 8 and non-real-time applications (graystripe) 9. This categorization is performed at each communication node 7which is to be encountered. Each data packet 6 which has been assignedto a real-time application is forwarded to the next communication node 7immediately without buffer storage. Data packets 6 without any real-timerequirement can be buffer stored in queues and forwarded from the queuein line with a particular reading mechanism. This reading mechanism candistribute the available resources for the total data packets 6 fromnon-real-time applications or for portions thereof according to apredefined scheme or can implement simple prioritization for the queues.In this case, the available resources for the data packets 6 fromnon-real-time applications are dependent on the instantaneous datavolume for the real-time applications.

1. A method for transmitting data from applications having differenttransmission requirements in a packet switched data communicationnetwork including communication nodes comprising: limiting eachapplication's data to a prescribed bit rate at a communication nodewhich is to be encountered when a respective application's data aretransmitted; creating and storing application specific contexts at thecommunication nodes which are to be encountered when a respectiveapplication's data are transmitted; reserving transmission resources atthe communication nodes which are to be encountered when a respectiveapplication's data are transmitted, in line with the applicationspecific contexts; and forwarding each application's data thecommunication node which is to be encountered by a respectiveapplication to a further communication node which is to be encountered,in line with the application specific contexts.
 2. The method as claimedin claim 1, wherein limiting is performed at an access communicationnode into the packet switched data communication network.
 3. The methodas claimed in claim 1, wherein each application's data are limited to aprescribed bit rate by measuring a volume of the respectiveapplication's data over a settable time interval in parallel withforwarding of the data and comparing it with the volume of data whichcorresponds to the prescribed bit rate.
 4. The method as claimed inclaim 1, wherein reserving is performed for data from applications whichrequire transmission in real time.
 5. The method as claimed in claim 1,wherein reserving involves each communication node which is to beencountered by a respective application's data using a guaranteed bitrate, required by the respective application, and a maximum supportablebit rate to derive a bandwidth value for a transmission resource whichis to be reserved, and reserving the transmission resource.
 6. Themethod as claimed in claim 1, wherein when the application specificcontexts are created at each communication node, the ratio of aguaranteed bit rate required by the respective application and a maximumsupportable bit rate can be varied.
 7. The method as claimed in claim 1,wherein a particular share of transmission resources from totaltransmission resources is reserved for data from applications whichrespectively require transmission in real time.
 8. The method as claimedin claim 7, wherein the share of transmission resources which isreserved for data from applications which respectively requiretransmission in real time is chosen to be smaller than a total quantityof transmission resources.
 9. The method as claimed in claim 1, whereinforwarding includes the applications' data being classified into atleast two categories in line with the application specific contexts andbeing forwarded in line with these categories.
 10. The method as claimedin claim 9, wherein the two categories correspond to classification intoreal-time applications and non-real-time applications.